The two most commonly used frequency bands set aside for cell phone use, are the AMPS band which extends between 824 and 896 MHz, and the PCS band, which extends from 1850 to 1990 MHz. It is noted that there is also a Nextel band of 806 to 866 MHz, which primarily overlap the AMPS band. The center of the lower frequencies is about 850 MHz while the center of the higher frequencies is about 1920 MHz. Cell phones are often used in vehicles, where much of the signal is lost due to the metal vehicle body. The losses can be greatly reduced by extending a coaxial cable from a cell phone to a window mount that mounts on a window such as the rear window of an automobile, and which couples through the window to an outside antenna. The inner window coupler preferably has a resonance in the band of frequencies to be transmitted, which results in transmission of a high percentage of the signal to and from the cell phone. The window coupling must be small, as with a rectangular box of no more than about two inches on each side, to avoid blocking a substantial portion of the window that it mounts on. When mounting on a rear window with antenna and/or defrosting wires embedded therein, it is desirable that the window coupler be mounted for minimum interference.
Window couplings are available that are resonant to either the low frequency bands of about 850 MHz or to the high frequency band of about 1920 MHz. It is possible to sell two type of window couplers that are each resonant to a particular band, but cell phone users often do not know what frequency their cell phones operate on. Thus, there is a need for cell phone couplers that are resonant at both the lower frequency of about 850 MHz and the higher frequency of about 1920 MHz, so they can be used with any common cell phone. The window coupler should be of simple construction, low cost and of small size.
In accordance with one embodiment of the present invention, inner and outer window couplers are provided for transmitting signals received through a coaxial cable from an inside cell phone or other transceiver, to an outside antenna, where the window couplers are of low cost and size and can efficiently couple two widely different frequencies. The inside or inner window coupler includes an inner metal plate for lying facewise adjacent to the window and a metal box device with a bottom wall spaced from the inner plate and facing it and with side walls extending outwardly to locations surrounding the inner plate. The inner plate has a plurality of corners and a plurality of sides extending between adjacent corners. This enable a resonance for each of two widely different frequencies, each obtained by a distance around the plate from a location where the inner conductor of the coax cable is connected to one of the corners.
In one inner window coupler, a quarter wavelength for the 1920 MHz band to obtain a resonance, approximately equals the length from the location where the inner coax conductor connects to the periphery of the plate, around a first corner and to a second corner. At the same time, a quarter wavelength for resonance at the 850 MHz band approximately equals the distance around the entire periphery of the plate. This results in a dual frequency inner window coupler of minimum size.
The outer window coupler includes a one-piece metal coupler with a plate part, a post part extending away from the plate part, and a pivot mount part. The lower end of the antenna is pivotally mounted about a horizontal axis on the pivot mount part and can be clamped in any orientation.
The novel features of the invention are set forth with particularity in the appended claims. The invention will be best understood from the following description when read in conjunction with the accompanying drawings.